Comments & required props

src/TabComplete.js

@@ -48,7 +48,12 @@ class TabComplete {
         this.isFirstWord = false; // true if you tab-complete on the first word
         this.enterTabCompleteTimerId = null;
         this.inPassiveMode = false;
+
+        // Map tracking ordering of the room members.
+        // userId: integer, highest comes first.
         this.memberTabOrder = {};
+
+        // monotonically increasing counter used for tracking ordering of members
         this.memberOrderSeq = 0;
     }
 

src/components/structures/RoomStatusBar.js

@@ -28,7 +28,7 @@ module.exports = React.createClass({
         room: React.PropTypes.object.isRequired,
 
         // a TabComplete object
-        tabComplete: React.PropTypes.object,
+        tabComplete: React.PropTypes.object.isRequired,
 
         // the number of messages which have arrived since we've been scrolled up
         numUnreadMessages: React.PropTypes.number,